As is known, painting with paint powders is carried out by spraying the paint powders, which may or may not be electrostatically charged, onto the product to be painted making use of appropriate spraying devices. Spraying is generally carried out in a booth through which the products to be painted are caused to pass.
Within each booth it is possible, inter alia, to intercept the paint powder which has not been deposited on the painted products. For this purpose, paint spray booths generally communicate with a suction unit comprising appropriate traps such as cyclone traps, filters and the like for the recovery of paint powder which has been sprayed but not utilised and is present in the air inside the booth.
The removal from each booth of paint which has not been removed by the suction unit and has stuck to the internal walls of the booth poses a problem which is more difficult to resolve. In addition, whenever it is desired to change the paint being used, for example to change to a different paint colour, the interior of the booth must be completely cleaned to avoid contamination and therefore substantial defects in the painted surfaces.
If carried out manually, correct cleaning of the interior of industrial paint spray booths takes a considerable amount of time, usually a few hours; cleaning is therefore very expensive in terms of labour costs and, in particular, the long down times which are entailed.
A number of solutions intended to partly automate the cleaning of booths have been proposed in the past to reduce down times. One of these solutions discloses a booth having a base equipped with scraper blades operated by a motor for the transportation of the paint powder to a removal aperture. Leaving aside the fact that a cabin of this type is structurally complicated and entails high production and operating costs, it does not provide a satisfactory solution to the problem outlined above since manual cleaning of the side walls of the booth ceiling is necessary.
Paint spray booths have also been designed with side walls and a base and ceiling formed by endless belts which may be displaced on return rollers, at least one of which is motorised. When the interior of the booth has to be cleaned, the endless belts are moved and carry the wall soiled with paint out of the booth and simultaneously replace it with a clean wall. In this case, it is necessary, however, to provide a suction device and possibly a scraper outside of each endless belt to collect and remove the paint powder adhering to the endless belt section which has just emerged or is emerging from the booth. This leads to a relatively complex structure entailing high operating costs which is unable to carry out satisfactory cleaning.
A paint spray booth with side walls formed by an unrolled and suspended belt which has to be rewound and disposed of when it is desired to change to a different paint or a different colour in the booth has also been proposed. This solution substantially reduces cleaning times for the booth, but the booth still requires costly accessories for the cleaning of the floor and/or ceiling.
US-A-3 811 371 discloses the use of a filter material as a side wall of the booth, air being extracted from the booth through the filter material. The filter material is mounted between a supply station and a receiving station and a new length of filter material is placed in position to define the wall when the original length becomes laden with paint. No attempt is made to provide a renewable coating for the ceiling or floor of the booth.
US-A-4 323 030 discloses endless belts defining the ceiling and side walls of a chamber, the endless belts being of non-permeable material, a portion of which being moved from an operative position defining the chamber to a non-operative position in which it is cleaned, readied for re-use. It may not be a practical proposition to re-use cleaned lining material and the described apparatus describes a filter material defining the floor of the chamber through which air is drawn as described in the preceding paragraph.
DE-OS 2 704 497 describes a paint spray booth comprising a framework, a supply of sheet material, a sheet material station, and means for guiding said sheet material from the supply to the receiving station along a path which defines the side walls of the spray chamber. The path does not define the floor of the chamber, over which is provided a separate filter belt which is guided in an endless path along the floor, the chamber and over a suction cleaning trough. Thus separate drive arrangements have to be provided for the sheet material defining the side walls of the booth and the filter material defining the floor of the booth.
An object of the present invention is to provide an industrial spray booth for the application of paint powders which may be cleaned in a very simple and more or less automatic manner with minimal down or dwell times of a few minutes.
A further object of the present invention is to design the booth such that it enables the continuous removal of the majority of the paint powder which collects therein during use without the need for complicated or costly appliances or devices for correct operation.